Jason Collins in interview with ABC News: Mind-boggling' to be first

In this photo provided by ABC, NBA basketball veteran Jason Collins, left, poses for a photo with television journalist George Stephanopoulos, Monday, April 29, 2013, in Los Angeles. In a first-person article posted Monday on Sports Illustrated's website, Collins became the first active player in one of four major U.S. professional sports leagues to come out as gay. He participated in an exclusive interview with Stephanopoulos, which is scheduled to air on Good Morning America on Tuesday. (AP Photo/ABC, Eric McCandless)